The invention relates to a bicycle, comprising a first frame part connected to a second frame part, which second frame part is provided with a drive, comprising a crankshaft carrying a driving gear blade and a rear axle carrying a driven gear blade and a gear mechanism for setting the transmission ratio between the crankshaft and the rear axle.
Such bicycle is known from EP 0 505 598. EP0 505 598 describes a bicycle, in particular suitable for adults, whose frame has a compact construction, as a result of which the bicycle occupies little space when not used. In the known bicycle, the gear mechanism is comprised with a free, rigid axle carrying a first, input gear blade or pinion that is coupled to the driving gear blade and which rigid axle further carries a second, output gear blade or crown wheel that is coupled via a derailleur to the rear axle carrying a number of drivable gear blades. In the known bicycle, the free rigid axle of the gear mechanism provides for a fixed transmission ratio between the input gear blade and the output gear blade, enabling a fixed reduction between the crankshaft and the rear axle. The derailleur is used to set the transmission ratio between the crankshaft and the rear axle.
A drawback of the known bicycle is that the derailleur mechanism occupies relatively much space. In particular, at the extreme transmission ratio, the maximally allowable obliquity of the chain between the gear blades of the free axle and the rear axle defines a relatively large minimal distance between the free axle and the rear axle. Further, the derailleur mechanism requires relatively much maintenance and the reliability in operation of the derailleur mechanism, when maintained insufficiently, is relatively low.
U.S. Pat. No. 3,979,136 also describes a foldable bicycle having a gear mechanism comprising a fixed, rigid axle carrying a gear mechanism providing for a fixed transmission ratio enabling a reduction between the crankshaft and the rear axle. A three speed settable hub is mounted in the rear wheel to set the transmission ratio between the crankshaft and the rear wheel.
The object of the invention is to provide a bicycle of the type mentioned in the preamble, in particular a compact bicycle having wheels of a relatively small diameter, which bicycle does not have the above-mentioned drawbacks.
To that end, a bicycle according to the invention is characterized in that the gear mechanism comprises a gear hub having a settable transmission ratio carrying a first, input gear blade coupled to the driving gear blade of the crankshaft and a second, output gear blade coupled to the driven gear blade of the rear axle, such that the transmission ratio between the first, input gear blade and the second, output gear blade can be set, which gear hub is mounted on the second frame part at a distance from the rear axle.
Through the use of the gear hub it is effected that the drive can be of a more compact design, while the reliability in operation can be increased and the maintenance can be limited. Moreover, the rear axle can now be constructed with only one gear wheel, so that a simpler rear axle can be used. It is further achieved that in the drive, a gear hub can be used that is normally accommodated in a rear wheel of a large diameter, that is, a diameter of 26 inch (66.04 cm) or 28 inch (71.12 cm). Since such gear hubs are already mass-produced and can be obtained relatively cheap, this reduces the costs of the bicycle considerably.
In another embodiment, a bicycle according to the invention is characterized in that the first frame part is connected to the second frame part for pivoting relative to a pivotal axis, such that the frame parts can pivot between an operating position of the bicycle in which the wheels of the bicycle are substantially in line, and a folded position of the bicycle in which the wheels are substantially located side by side.
Preferably, the pivotal axis extends substantially vertically and the first frame part carries a saddle, while the second frame part comprises a single supporting arm for the rear axle. It is thus achieved that in folded condition, the bicycle occupies little space, while the pedal drive is located entirely within the second frame part. This last facilitates the pivoting action between the operating position and the folded position and simplifies the construction of the bicycle.
It is observed that in this context, the expression that the gear hub is located at a distance from the rear axle should at least be understood to mean that the center line of the gear hub does not coincide with the center line of the rear axle.
The invention also relates to a pedal drive.